1. Field of the Invention
The present invention relates to dielectric films, and more particularly, to improved methods for forming such materials.
2. Description of the Related Art
Dielectric films and, more particularly, high dielectric constant (.epsilon.&gt;10) films, such as tantalum pentoxide (Ta.sub.2 O.sub.5), titanium oxide (TiO.sub.2), and barium strontium titanate ((Ba,Sr)TiO.sub.3 or BST), play an important role in the manufacturing of integrated circuits. Such films have applicability, for example, in the manufacture of metal-oxide-semiconductor (MOS) transistors as well as in the manufacture of metal-oxide-metal (MOM) and metal-insulator-metal (MIM) capacitors and amorphous semiconductors.
High dielectric constant films are generally formed by either sputtering or chemical vapor deposition (CVD). For several reasons, the preferred method, however, is CVD. For example, high dielectric constant films deposited using CVD are far less dense and, therefore, can be annealed at lower temperatures than sputtered films. Further, sputtered high dielectric constant films are typically oxygen deficient (or metal-rich). This is especially true in the interfacial regions between the electrode and the dielectric, as in the case of MOM and MIM capacitors. The oxygen deficiency that is typical of a sputtered high dielectric constant film generates pathways for electrical conduction (referred to as "leakage"). This leakage (and hence the oxygen deficiency that causes it) is considered a flaw in the film. In an attempt to remedy this flaw, post deposition annealing of the film in an oxygen ambient is usually required to incorporate oxygen into the film and thereby reduce the leakage by eliminating (or substantially eliminating) the oxygen deficiency. However, because of the dense nature of sputtered films, they are difficult to anneal.
Despite the foregoing disadvantages of sputtering, sputtering does have some advantages over CVD for forming high dielectric constant films. For example, with sputtering, there is more flexibility in varying the composition of dopants in the resultant film. Further, it is easier to change materials to be deposited by sputtering. Still further, sputtering involves fewer dangerous chemicals than CVD.